More than two years after his election to the Ukrainian parliament on a wave of popular anger over political and economic rot in the corridors of power, Oleksandr Onyshchenko, by his own account, got his hands plenty dirty.

The 47-year-old Onyshchenko insists he was a loyal political lieutenant of President Petro Poroshenko, serving as a middleman for the wartime president's inner circle, smearing a prime minister, and ensuring that bribes were paid in good order.

But it all came crashing down for the former Olympic equestrian-turned-politician in July, when his fellow lawmakers consented to the Ukrainian prosecutor-general's request to strip him of his parliamentary immunity to put him on trial for an alleged massive embezzlement scheme involving a state-owned gas company and millions in kickbacks.

Onyshchenko had fled Ukraine weeks earlier and has repeatedly proclaimed his innocence from abroad.

But his counterpunch at Kyiv landed earlier this month, just as the Ukrainian Security Service (SBU) launched a treason case against the fugitive legislator.

Onyshchenko told Current Time TV and other media from his self-exile -- he is reportedly seeking political asylum in the United Kingdom -- that he has damning recordings and digital evidence against Poroshenko.

He added that he has handed materials over to the FBI, which falls under the U.S. Department of Justice.

"I gave [the Americans] documents that confirm the corruption of President Poroshenko. That's all," Onyshchenko told Current Time TV,theRussian-language network run by RFE/RL and VOA, in a Skype interview on December 2. He asked that his location not be disclosed, saying he fears for his personal safety.

Oleksandr Onyshchenko spoke to Current Time TV via Skype from an undisclosed location.

Poroshenko's office on December 7 dismissed Onyshchenko's accusations as "absolutely false," telling RFE/RL: "They are the expedient fiction of the suspect."

The statement said that Ukrainian authorities suspect Onyshchenko of "having created an organized criminal group" that cost the state some 1.6 billion hryvnyas ($62 million).

"To avoid punishment," the presidential office added, "Mr. Onyshchenko tries to politicize his criminal case and pretends to be a victim of political repressions."

Onyshchenko’s accusations are extraordinary, even by the notorious standards of Ukrainian politics. And they are unusual in that he purportedly made audio recordings and kept SMS text messages during his time as a Poroshenko ally.

But what may be the most explosive element to this saga is Onyshchenko's claim that he turned over his materials to the U.S. Justice Department to investigate Poroshenko himself -- the man Washington and much of Europe have thrown their support behind to stabilize the country amid Russian aggression.

I was there with him for two years. I watched. I followed all negotiations that he did. ... I was on the president's team, directly fulfilling his orders."

-- Oleksandr Onyshchenko

"I was there with him for two years. I watched. I followed all negotiations that he did, with [Kyiv Mayor Vitaly] Klitschko [and] with many deputies," Onyshchenko said.

"I was on the president's team, directly fulfilling his orders," he added.

Poroshenko's office rejected any such cooperation in its December 7 statement, saying Onyshchenko "made up a story about 'membership in a team'" and added, "People of such reputation cannot be members of a team."

U.S. authorities have refused to comment on Onyshchenko's claim that he turned over documents or audio recordings. The U.S. Embassy in Kyiv referred all questions to the U.S. Justice Department.

In Washington, Justice Department spokesman Peter Carr refused to confirm or deny specifically whether the department had received any materials or met with Onyshchenko.

"Speaking generally, it is common for individuals to request to meet with the Justice Department to provide information -- and while department prosecutors and law-enforcement agents will attempt to meet to gather potential information on alleged violations of U.S. law, the mere fact of a meeting is not an indication that such violations have occurred or that the individual’s information is considered to be accurate," Carr told RFE/RL in an e-mail.

The office of Ukrainian President Petro Poroshenko has dismissed the accusations as "absolutely false."

Ukraine's ambassador to the United States, Valeriy Chaly, declined to say whether he knew if Onyshchenko had indeed provided materials to the Justice Department.

Ukraine is regularly ranked among the most corrupt countries in the world and allegations of double dealing, inflated contracts, bribery, and other claims among business and political elites are common.

International financial institutions have warned Kyiv that its lack of reform and persistent corruption threaten billions in crucial aid that has helped keep the country afloat since its invasion by Russian forces to seize Crimea in 2014 and a continuing war against Russia-backed separatists in the Donetsk and Luhansk regions in eastern Ukraine.

To avoid punishment, Mr. Onyshchenko tries to politicize his criminal case and pretends to be a victim of political repressions."

-- Office Of President Petro Poroshenko

Poroshenko has also faced repeated allegations of corruption, many dating to business holdings that have included chocolate manufacturer Roshen and the Channel Five TV station.

The taint has led to the resignation of several prominent ministers and other leading officials who were brought in by Poroshenko to help clean up the country's books and its image.

In February, Lithuanian-born Economy Minister Aivaras Abromavicius announced his resignation, citing a "sharp escalation in efforts to block systemic and important reforms."

Mikheil Saakashvili, the boisterous former Georgian president who was brought on by Poroshenko to govern the Odesa region, resigned last month and accused Poroshenko of dishonesty and of sabotaging crucial reforms.

For his part, Onyshchenko entered parliament in 2014 as a member of Poroshenko’s political faction.

He reportedly fled the country in June amid word of a criminal investigation into his businesses, including an alleged huge natural-gas fraud at a state energy company.

In his interview with RFE/RL's Current Time TV, Onyshchenko said he was directly responsible for fulfilling Poroshenko’s orders.

He said that included a complex scheme to drive down the approval ratings of Ukraine's prime minister, Arseniy Yatsenyuk, to make way for a Poroshenko ally. Yatsenyuk was a technocrat respected by the West but seen in some Ukrainian business circles as an obstacle to the kind of shady side deals that flabbergast would-be reformers.

"During this period, it was necessary to shore up [Poroshenko's] power, since, when he became president, power was in effect held by the prime minister," Onyshchenko told Current Time TV. "That is, the entire cabinet practically answered to Yatsenyuk. Poroshenko, accordingly, considered Yatsenyuk his enemy, a person who bothers him, who interferes..."

Yatsenyuk resigned in April and was followed by Volodymyr Hroysman, a member of the ruling Petro Poroshenko Bloc seen by some as politically indebted to the president.

Poroshenko's popularity has waned as Ukrainians battle economic hardship fueled in part by Russia's land grab in Crimea and Kyiv's continuing fight against Russia-backed separatists.

Still, a November poll by the Kyiv-based Razumkov Center suggested that if presidential elections were held today in Ukraine, Poroshenko would lead vote-getters with around 16 percent, followed by former Orange Revolution leader and ex-Prime Minister Yulia Tymoshenko (11.5 percent) and former Energy Minister and Opposition Bloc leader Yuriy Boyko (9.4 percent).

Based on an interview for Current Time TV by Timur Olevskiy and Saken Aymurzaev, with reporting by RFE/RL correspondents Christopher Miller in Kyiv and Mike Eckel in Washington and contributions by Andy Heil in Prague